This invention relates to a new process for the production of polyethers terminated by aminophenoxy groups, to the polyethers obtained by this process and to their use as reactants for organic polyisocyanates in the production of plastics containing urea groups by the isocyanate polyaddition process.
Polyethers terminated by aminophenoxy groups are valuable starting materials for the production of plastics by the isocyanate polyaddition process. The production of such compounds is described, for example, in EP-A-0,268,849, EP-A-0,288,825 or EP-A-0,335,274.
Basically, the processes according to these prior publications comprise reacting hydroxyl-terminated polyethers, i.e. the polyether polyols known from polyurethane chemistry, with halogen- or alkoxy-substituted nitrobenzenes in the presence of compounds showing an alkaline reaction, to form the corresponding nitrophenoxy-substituted polyethers and subsequently hydrogenating the nitro group to amino groups.
Applicants' own tests have shown that polyether diols which have been produced by polymerization of tetrahydrofuran (THF) are difficult to react, in accordance with this principle to form the corresponding nitrophenyl-terminated compounds, or they can only be correspondingly reacted using polar aprotic solvents, such as for example dimethyl sulfoxide, N-methyl pyrrolidone or dimethyl formamide. However, it would be desirable if these solvents could be replaced by physiologically safer and less expensive solvents, such as for example toluene or xylene, or better still if inert solvents could be dispensed with altogether.